Wave guiding system and method



Aug. 7, 1962 J. J. DRUM WAVE GUIDING SYSTEM AND METHOD 2 Sheets-Sheet 1 Filed July 27, 1959 SECOND CIRCUIT FIG. 2b.

lNVENTOR: JOHN J. DRUM, BY W a HIS ATTORNEY.

1962 J. J. DRUM 3,048,804

WAVE GUIDING SYSTEM AND METHOD Filed July 27, 1959 2 Sheets-Sheet 2 CIRgUIT I 1 I e I l l l 2 3 J I ,m 7/ ..ll CIRCUIT I CIRCUIT FIG.3b.

INVENTORI JOHN J. DRUM HIS ATTORNEY.

United States Patent Ofiflce 3,48,804 Patented Aug. 7., 1962 3,048,804 WAVE GUIDING SYSTEM AND METHOD John J. Drum, Fayetteville, N.Y., assignor to General Electric Company, a corporation of New York Filed July 27, 1959, Ser. No. 829,825 3 Claims. (Cl. 333-98) This invention relates primarily to wave transmission method and means, and particularly to method and means for controlling electromagnetic waves.

In that branch of the electronics industry where waveguide is used as a medium for the transmission of electromagnetic waves, there exists a need for devices which are capable of discriminating between electromagnetic Waves of different configuration or mode. Prior arrangements for serving these needs have been limited in usefulness because of the property of merely reflecting certain of the modes, or because of low power capacity, narrow bandwidth, etc. A relatively simple device capable of overcoming these limitations is a highly desirable addition to the art.

It is therefore an object of this invention to provide an improved wave controlling system and method.

Another object of this invention is to provide an improved electromagnetic wave mode filter, which is essentially reflection-less, and which is suitable for high-power operation.

Another object of this invention is to provide an improved signal processing method and means.

Another object of this invention is to provide an improved method for diplexing two waves in round waveguide, wherein the two waves are of the same fundamental mode, but of orthogonal polarization.

Another object of this invention is to provide an improved method and means for selectively coupling waves of certain modes out of a given waveguide section, while permitting waves of other modes to pass unrestricted through the waveguide section.

In accordance with one embodiment of the invention, an arrangement is provided for selectively coupling waves of a desired mode between a first and a second circuit while discriminating against coupling of waves of undesired mode. The arrangement employs a septum, formed of an electrically conductive material, and positioned at the junction of two waveguide sections. The first said waveguide section provides coupling for the desired mode between the first circuit and the second circuit. The septum is positioned such that it is perpendicular to the electric field vector associated with the waves of the desired mode, which permits these waves to be passed from said first circuit to said second circuit effectively without reflection. The undesired mode, having electric field components parallel to the septum, will be reflected at the leading edge of said septum. The leading edge of said septum is oriented at such an nagle that the undesired modes are reflected into the second waveguide section and dissipated.

The novel features which are believed to be characteristic of this invention are set forth with particularity in the appended claims. This invention itself, however, both as to its organization and method of operation, together with further objects and advantages thereof, may best be understood by reference to the following description taken in connection with the accompanying drawings in which;

FIG. 1 illustrates in part section and in part schematic form an embodiment of the present invention useful for selectively coupling waves of desired mode between a pair of waveguide sections while effectively preventing the coupling of waves of undesired mode;

FIGS. 2a and 2b illustrate in part section and in part schematic form an application of the present invention to an arrangement involving waveguides of difierent crosssectional dimension;

FIGS. 3a and 3b illustrate in part section and in part schematic form a further embodiment of the present invention wherein waves of undesired mode are reflected into a plurality of separate channels, and by means of a plurality of septa;

FIGS. 4a and 4b illustrate an application of the present invention to circular waveguides.

Referring to FIG. 1, there is shown a first circuit, or source 1, providing a plurality of electrical waves occurring in different modes. For example, the electromagnetic waves may comprise a component of fundamental frequency and desired mode and a plurality of components harmonically related to the fundamental frequency and occurring in a plurality of undesired modes. It is desired to couple only the waves of fundamental frequency and desired mode from the first circuit to a second circuit 2 which may comprise an output or a load circuit. Furthermore, it is desired to prevent waves of undesired mode available from first circuit 1 to be coupled to the second circuit. Briefly, this is accomplished by using a first waveguide section 3 interconnecting said first and second circuits. In accordance with the invention, a septum 4 is provided for reflecting waves arriving from the first circuit to a third circuit 5 by way of a second waveguide section 6. The septum 4 is so dimensioned and positioned at the junction of waveguide sections 3 and 6, that waves of desired mode are coupled between the first and second circuits while waves of the undesired mode are coupled between the first and third circuits. The dimensioning and positioning are as follows: The septum 4 comprises a sheet of electrically conductive material such as brass, aluminum, etc. The sheet is positioned in the waveguide section 3 at the junction with the waveguide section 6 such that it is perpendicular to the electric field vector 7 associated with the component of the wave of desired mode and parallel to the electric field vector 8 shown in dotted form associated with the component of wave of undesired mode. septum and is coupled to the second circuit as shown at 7. The component of wave of undesired mode, having its electric field vector parallel to the electrically conductive sheet 4, is reflected into the second waveguide section 6 for coupling to the third circuit 5 as shown at 8'. To the extent that some portion of the component of desired mode is coupled into the waveguide section 6, posts 9 and 10 are provided to minimize this effect. The positioning and other characteristics of such posts are well known and it is suflicient to state that they operate to effectively show a short circuit at the entrance to waveguide 6 for waves of said desired mode.

Referring to FIG. 212, there is shown a cross-sectional view of a septum similar to that shown in FIG. 1. However, the section view taken across AA indicates that the first waveguide section 3 comprises two waveguide portions 11 and 12 of different cross-sectional dimension. In the case of the rectangular guide, FIG. 2b illustrates that the height of section 11 is greater than that for section 12. FIG. 2b shows the stepped or tapered reduction in the waveguide size shown at 13 in relation to the positioning of the septum 14.

FIGS. 3a and 3b illustrate a further embodiment of the invention wherein waves of undesired mode are reflected into a plurality of circuits shown as 5 and 5. In this connection the septa of electrically conductive material, shown at 14, have leading edges cut such that the portion of the waves of undesired mode are reflected into the circuits 5 and 5 While waves of the desired mode are coupled through to the second circuit. Waves of the desired mode cannot couple to circuits 5 and 5' because of the cutoff frequency characteristic of Waveguide sections 6 The electric field vector 7 propagates past the and 6'. FIG. 3b illustrates the use of a plurality of septa positioned at the junction to accomplish the mode filtering. By resorting to more septa, higher frequency modes can be filtered by a process of reflection and absorption as previously indicated.

FIGS. 4a and 4b illustrate an application of the invention to circular waveguides. In FIG. 4a waves of desired mode 7 are propagated past the septum and arrive as Waves with an E field vector 7, While the electric field vector associated with waves of the undesired mode 8 is coupled into the second waveguide section and appears as 8'. The device represented in FIGS. 4a and 4b can readily be used as a diplexer, wherein vectors 7 and 3 represent waves of the same fundamental mode, but of orthogonal polarities. In this application the invention serves as a means of combining, or separating, the two waves.

While a specific embodiment has been shown and described, it will of course be understood that various modifications may yet be devised by those skilled in the art which will embody the principles of the invention and found in the true spirit and scope thereof.

What I claim and desire to secure by Letters Patent of the United States is:

1. A source of waves of desired and undesired mode, a first output circuit, a second output circuit, a first waveguide for coupling said waves of desired and undesired mode from said source to said first output circuit, a second waveguide connecting with said first waveguide section at a junction, said second waveguide having a longitudinal axis extending perpendicularly to the longitudinal axis of said first waveguide, an electrically conductive septum positioned at the junction of said first and second waveguides, said septum positioned at said junction perpendicular to the electric field vector associated with the waves of said desired mode such that said Waves of desired mode are coupled to said first output circuit, said waves of second mode having component electric fields parallel to said septum, said septum oriented in a plane parallel to the longitudinal axis of said second waveguide, the leading edge of said septum being oriented at such an angle that said waves of second mode are refiected into said second output circuit.

2. In combination, a source of waves of desired and undesired mode, an output circuit, a first waveguide section for coupling waves from said source to said output circuit, a second waveguide section connected to said first waveguide section at a junction, said second waveguide having a longitudinal axis extending perpendicular to the longitudinal axis of said first waveguide, a septum comprising a sheet of electrically conductive material positioned at said junction, said sheet being perpendicular to the electric field vector associated with said waves of desired mode whereby said waves of desired mode are coupled to said output circuit, said septum being oriented in a plane parallel to the longitudinal axis of said second waveguide, the leading edge of said sheet making an angle with the direction of propagation of said waves having a component electric field parallel to said sheet such that waves of undesired mode are reflected into said second waveguide.

3. A first circuit, a second circuit and a third circuit, a first rectangular waveguide for propagating waves of a first and a second mode having orthogonally related electric field vectors associated therewith from said first circuit toward said second circuit, a second rectangular waveguide connecting with said first waveguide at a junction intermediate said first and second circuits, said second waveguide having a longitudinal axis extending perpendicular to the longitudinal axis of said first waveguide, an electrically conductive septum positioned at the junction of said first and second waveguides oriented in a plane parallel to the longitudinal axis of said second waveguide and having its plane perpendicular to the electric field vector associated with the waves of said first mode such that said waves of said first mode are propagated to said second circuit from said first circuit, said septum having its leading edge oriented at such an angle to the direction of arrival of said waves of said second mode from said first circuit such that said waves of second mode are reflected by said septum into said third circuit.

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